Thyfault, PhD, is an associate professor at Kansas University Medical Center, where he studies the health effects of exercise. Each year, he travels to the American Diabetes Association's annual scientific sessions. The meeting attracts roughly 18,000 people and is held in massive convention centers that span the distances of several football fields, their floors connected by long staircases and humming escalators.

Conference organizers pick a prominent set of stairs and lay down a decal with the logo for their "Stop Diabetes" campaign -- a hand with a drop of blood on the fingertip. It's meant to remind attendees to take the stairs instead of riding the escalator.

Each time they put the sign up, Thyfault stands at the foot of the stairs and whips out his smartphone. The stairs are nearly empty, but the escalator is packed. To him, it's a picture worth a thousand pills.

"Exercise and physical activity is not something that you just do extra in your life to get extra healthy. Rather, it's something that's absolutely necessary for normal function," he says.

Thyfault hopes to make more people aware that exercise benefits the body in ways that go far beyond muscle tissue and burning fat.

"We were meant to exercise quite a bit every day to survive, and now we've taken it away, and we're actually causing dysfunction," he says.

Exercise and Blood Sugar

He's passionate about exercise because his research has shown again and again how critical it is to health. He says when he's tried to cause disease, for example, by feeding rats or mice high-fat diets, he can't do it as long as the animals are exercising.

"Inactivity is the foundational piece that has to be there for these diseases to develop," he says.

In one experiment, for example, he took healthy people who were walking at least 10,000 steps a day and asked them to walk less -- around 5,000 steps a day, about as much exercise as the average American gets.

Thyfault quickly saw changes in how well their blood vessels worked and how well they could control their blood sugar after meals. The study participants looked like they were on their way to getting type 2 diabetes.

"What we think is that if that level of activity continues for a prolonged period of time, disease develops," he says.

In fact, a long-running study sponsored by the government, called the Diabetes Prevention Program, tested this. It split more than 3,000 overweight adults with prediabetes into three groups. The first group got a lot of help to eat better and exercise more, with a goal of 150 minutes a week. The second group took the drug metformin, which helps the body respond better to the hormone insulin. The third group took placebo pills.

Exercise and a healthy diet worked better than the pill. After 4 years, compared to the placebo group, the people who ate better and exercised cut their risk of getting diabetes by about twice as much as the group taking medication -- a 58% reduced risk of getting diabetes compared to 31% in the medication group.

Exercise and Fat

Laurie J. Goodyear, PhD, is a senior investigator at Joslin Diabetes Center and an associate professor at Harvard Medical School. She is studying the effect of exercise on fat, specifically the layer of white fat that sits just under the skin.

Most people know that exercise burns fat. It's the reason most people hit the treadmill in the first place.

But fat isn't just a place we park extra calories. "The tissue has a lot of other properties," she says.

"Exercise really makes fat healthier and helps it burn more energy."

Specifically, she says, exercise shrinks the size of individual fat cells, and the cells develop more energy-producing parts called mitochondria.

That means that fat tissue is burning more calories, even at rest, Goodyear says.

In one experiment, she took white fat from exercise-trained mice and transplanted it into inactive mice. Nine days later, those mice had better blood sugar control and their bodies responded better to insulin than mice that got fat from other inactive mice. What's more, transplanted fat from exercised mice completely reversed the negative effects of eating a high-fat diet.

"What we've realized is that fat isn't simply storage," she says. "We see about 4,000 genes in fat tissue change with exercise. It's not just that fat cells get smaller."

Exercise, Blood Vessels, and the Brain

Exercise also affects the lining of blood vessels, a layer of tissue called the endothelium that's just a single cell thick. When this layer of tissue is damaged, it's easier for dangerous blood clots to form.

Michael D Brown, PhD, a professor of kinesiology and nutrition at the University of Illinois at Chicago, has discovered that when the body is inactive, the cells in the endothelium get sluggish and don't sit in the vessel wall properly. But exercise, which causes blood to flow more swiftly and under greater pressure, realigns the cells.

About 12 hours after a single bout of exercise, the cells have repositioned themselves to be in line with the flow of blood. This helps blood vessels work better, keeping them open and elastic, rather than stiff, narrow, and clogged.

In the brain, recent studies have shown that physical activity makes the brain more connected by bulking up the white matter, the wiring that transmits signals between nerve cells. And older adults who exercise have more gray matter in areas of the brain responsible for self-control, memory, and decision making.

Exercise also beats medication for some ailments. In head-to-head tests, it works as well or better than pills for depression. In other conditions, like Alzheimer's and arthritis, it's been shown to delay disability.

It's enough to convince anyone to lace up. Or at least it should be.

Yet that message seems to be falling on deaf ears. This year's survey by the Physical Activity Council found that 28% of Americans say they are totally inactive. It's the highest level of physical inactivity measured by the survey since 2007.

Thyfault takes this personally. His 42-year-old father died of a heart attack when Thyfault was just 3. He has two young sons of his own, and he doesn't want to leave them prematurely.

To keep himself healthy, he tracks his own steps every day.

"I'm kind of obsessive about it," he says.

If you're ready to get going but not sure where to start, Thyfault recommends three levels of fitness.

He says level one is just to walk and keep track of your steps. You can do this with a trendy fitness tracker, but even an inexpensive pedometer or a smartphone app will do the trick. Your goal should be at least 8,000 steps a day.

Once you're hitting that goal on a regular basis, level two is to do three to five defined exercise sessions each week, with a goal of 30 to 45 minutes of aerobic activity -- like running or pedaling on an elliptical -- each time.

Level three is to add a couple of days of resistance training each week.

Goodyear agrees and says getting more exercise will make a difference you can feel.

"I always feel that if I'm consistently exercising I have more energy. People sleep better when they exercise routinely, and then your body just becomes more efficient," she says.